This invention relates to a sweep or ramp generator useful in conjunction with a television kinescope deflection arrangement.
A television vertical oscillator and deflection apparatus is shown in U.S. Pat. No. 3,735,192 issued on May 22, 1973 to Leslie Avery. This vertical deflection generator includes two charging capacitors coupled in series and to ground through a small resistor. Charging current is supplied to the capacitors from B+ through a resistance. A further charging current is provided for one of the capacitors by a further resistance driven by the voltage across one of the capacitors. During retrace, the series-coupled capacitors are discharged through the collector-to-emitter path of a switched transistor driven by a multivibrator synchronized with the horizontal synchronizing pulses. The ramp voltage appearing across the series-coupled capacitors drives a kinescope deflection coil through an output amplifier.
U.S. patent application Ser. No. 595,809, filed July 14, 1975 for Peter Eduard Haferl and entitled "SWITCHED VERTICAL DEFLECTION SYSTEM", now U.S. Pat. No. 4,048,544 describes a switched synchronous vertical deflection (SSVD) circuit in which the energy for the vertical deflection system is derived from the horizontal deflection system by means of switched reactances. The switched reactances are coupled to the horizontal deflection generator and operated during the horizontal retrace interval as a deflection amplifier. The SSVD arrangement is economically advantageous. However, it has been discovered that high-frequency components of the driving sawtooth or ramp retrace may cause undesirable ringing of the SSVD amplifier.
It is economically desirable to form the vertical sawtooth generator on a monolithic integrated circuit. It is also desirable to have a single type of integrated circuit adaptable for use with large numbers of different television receiver types and having different kinescope sizes and deflection yokes. Since the vertical retrace or flyback times are different for different yokes, it is desirable that such an integrated circuit have a retrace time which is easily and conveniently externally adjustable with suitable accuracy.
Since high-tolerance resistors cannot presently be fabricated economically in integrated-circuit form, it is necessary that the charging capacitors be charged from an external resistor. However, for purposes relating to raster linearity it is desirable that a voltage having a value equal to that at a point along the charging resistor be fed to the junction of the charging capacitors. This should be accomplished with a minimum number of interface terminals between the monolithic integrated circuit and external circuits.